This invention is directed to a grinding wheel and particularly to a grinding wheel which contains an automatically adjustable support plate or tool rest member.
Grinding wheels are regularly employed for removing burrs from work pieces, for sharpening tools, for polishing metal and the like. Most every manufacturing company has at least one grinding wheel available for use by its employees. Grinding wheels currently in use are generally of the type having a manually adjustable tool rest member as depicted on the right-hand side of FIG. 1.
One or two grinding wheels are fixed at each end of a rotatable shaft operatively connected to an electric motor. A tool rest member is mounted in front of the grinding wheel to provide a firm base upon which a work piece can be rested during the grinding operation. As shown on the right-hand side of FIG. 1, the tool rest member is of the type which can be manually adjusted and slidably moved towards the grinding wheel by loosening a set screw affixed to the base thereof. As the grinding wheel becomes worn and its size reduced, the set screw is loosened and the tool rest member is manually moved towards the grinding wheel. It is essential that the tool rest member be positioned as close to the grinding wheel as is possible to prevent the work piece from being drawn into the space between the grinding wheel and the tool rest member. If the work piece is forced into the space between the grinding wheel and the tool rest member, the operator can lose control of the work piece and, in all probability, damage either the work piece or the grinding wheel.
Although adjustment of the tool rest member requires very little time and effort, it has been found that most users will generally attempt to use the grinding wheel without first adjusting the tool rest member. Even if the tool rest member is readjusted, it is usually done in a hurried fashion and, as a result, may be improperly done. As the grinding wheel becomes worn from continuous use, the space between the edge of the grinding wheel and the tool rest member increases. As pointed out above, when this occurs the use of the grinding wheel can become dangerous and can cause irreparable injury to the work piece, the grinding wheel or the operator. As the space between the grinding wheel and the tool rest member is increased, the possibility that the work piece will be forced into the space is substantially increased. Although damage to the work piece and the grinding wheel is most likely, missile-like fragmentary pieces from the damaged work piece or from the grinding wheel can be released and cause permanent injury to the operator.
In addition to the dangers above mentioned, most grinding wheels are constructed such that the inner part or section of the wheel does not possess the same degree of hardness as does the outer section. Thus, when the wheel becomes worn and approaches the softer inner section, it should be replaced. Most grinding wheel manufacturers indicate this point on the grinding wheel by placing a circular label along the side of each face of the grinding wheel. Instructions are provided by the manufacturer which state in effect that the use of a grinding wheel should be discontinued before the wheel reaches this minimum diameter. In many cases, an operator will attempt to use the grinding wheel just one more time before changing the wheel. In so doing, the possibility of injury to the operator is substantially increased.
In order to avoid the problem areas above-mentioned it is a primary object of this invention to provide a grinding wheel and tool rest member which will automatically maintain an optimum safe distance between the grinding wheel and tool rest member. Another object of this invention is to provide a grinding wheel which is adapted with a sensing means which will automatically move the tool rest member toward the grinding wheel as the wheel becomes worn and thereby maintain a proper and safe spacing therebetween.
Still another object of this invention is to provide an automaticc cut-off switch which will terminate power to the grinding wheel whenever the wheel becomes worn and approaches its critical minimum diameter.